With Manufacturer's Scan Tool
Fuel Pump, Checking
Special tools, equipment, test and inspection devices; required accessories
- 3217 ring nut wrench
- VAG 1318 pressure meter
- VAG 1318/1 pressure gauge adapter
- VAG 1318/11 adapter
- VAG 1318/17 adapter
- VAG 1318/23 adapter
- VAG 1348 comparison meter
- VAG 1466 A electrical circuit tester
- VAG 1527B voltage tester
- VAG 1594 A auxiliary measuring tools-set
- VAG 1715 Multimeter
- Measuring vessel
- Wiring diagram
Test conditions
- Fuse No. 28 OK
- The battery voltage must be at least 11.5 V.
Checking operation and power supply
- Fold rear seat bench forward.
- Remove cover of fuel delivery module.
- Briefly actuate starter. Fuel pump should be running audibly.
- Turn off ignition.
If the fuel pump does not function:
- Remove cover of fuse carrier.
- Remove fuse no. 28 from fuse carrier.
- Connect VAG 1348/3A remote control with VAG 1348/3-2 adapter cable at contact 28a to fuel pump and battery positive (+) terminal.
- Actuate remote control.
If the fuel pump is running:
- Use VAG 1466 A to check that fuel pump relay operates according to wiring diagram:
If the fuel pump is not running:
- Remove 4-way connector -arrow- from flange.
- Connect VAG 1527 B diode test lamp to plug external contacts using auxiliary cables from VAG 1594 A.
- Actuate remote control. LED should illuminate.
If the LED does not illuminate:
- Use wiring diagram to find and repair broken connection:
If the LED illuminates (power supply OK):
- Remove union nut with wrench 3217.
- Check whether electrical wires between flange and fuel pump are connected.
If no broken connection can be determined, the fuel pump is faulty:
- Replace fuel delivery module.
Checking capacity
Test conditions
- Power supply OK
- VAG 1348/3A remote control is connected
Test sequence
- Remove cover from fuel filler neck.
- Remove feed line -3- and use a clean rag to catch fuel flowing out.
NOTE: Press the tabs on the hose couplings together for this.
CAUTION!
The feed line is underpressure! Place clean rags around the hose connections, then reduce the pressure by disconnecting the hose very slowly and carefully.
- Connect VAG 1318 pressure measuring device VAG 1318 with VAG 1318/23 adapter, and connect VAG 1318/17 to feed line.
- Place VAG 1318/1 hose on pressure meter VAG 1318/11 adapter and hold it in a measuring vessel.
- Open pressure meter shut-off valve. Lever will then be pointing in direction of flow -A-.
- Actuate VAG 1348/3A remote control. Simultaneously, close shut-off valve slowly until manometer reads 3 bars of positive pressure. Do not change shut-off valve setting any more.
- Empty measuring vessel.
- The fuel pump capacity depends on battery voltage. Therefore connect multimeter to battery using auxiliary cables from VAG 1594 A.
- Actuate remote control for 30 seconds and measure battery voltage simultaneously.
- Compare fuel flow with specification.
*) Minimum capacity cubic cm/30 s
**) Voltage at fuel pump when motor is off but pump is running (approx. 2 volts less than battery voltage).
Example:
During the test, the voltage of the battery was measured as 12.5 volts. Since the pump voltage is approximately 2 volts lower than that of the battery, a minimum capacity of 200 cubic cm/30 s results.
If the minimum capacity is not achieved:
- Check fuel lines for possible restrictions (kinks) or blockages.
- Pull feed hose -1- from fuel filter inlet.
NOTE: Press the tabs on the hose couplings together for this.
CAUTION!
The feed line is underpressure! Place clean rags around the hose connections, then reduce the pressure by disconnecting the hose very slowly and carefully.
- Connect VAG 1318 pressure measuring device with 1318/17 adapter on hose.
- Test capacity over again.
If the minimum capacity is not achieved this time:
- Replace fuel filter.
If the minimum capacity is not achieved once again:
- Remove fuel delivery module and check whether filter strainer is dirty.
Only if no error was found to this point:
- Replace fuel delivery module.
If you achieved the required capacity but still suspect a problem in the fuel supply anyway (e.g. intermittent failure of the supply):
- Check pump current consumption as follows:
- Reconnect all unfastened lines.
- Using current probe, connect VAG 1715 multimeter to green/yellow wire in wiring harness.
- Turn on engine and let it idle.
- Measure pump current consumption.
Specification: max. 8 amperes
NOTE: If the problem in the fuel system is intermittent, the test can be conducted during a test drive. This requires a 2nd person.
If the current consumption was exceeded:
- The fuel pump is defective, replace fuel delivery module.
Checking pump check valve
Test conditions
- The VAG 1348/3A remote control is still connected.
- The VAG 1318 pressure measuring device is still connected.
Test sequence
NOTE: This test simultaneously checks the integrity of the connections of pump feed line from the fuel delivery module to the connection point of the VAG 1318 pressure measuring device.
- Close pressure measuring device shut-off valve (lever perpendicular to direction of flow -arrow-).
- Actuate remote control at brief intervals until an pressure of approximately 3 bar has built-up.
CAUTION!
There is a danger of splashing when the shut-off valve is opened. Hold vessel in front of the open inlet of the gauge.
- Lower pressure that has built-up too high by opening shut-off valve very carefully.
- Observe drop in pressure on manometer. Pressure may not drop below 2.5 bar after 10 minutes.
If the pressure continues to drop:
- Check line connections for proper sealing.
If no problem was found in the lines:
- Fuel pump is faulty; replace fuel delivery module.